Insulated conductor



y 21, 1929- H. D. SAYLOR INSULATED CONDUCTOR Filed Oct. 28, 1924 [NVENTOR H. D. 5/4 YLOR $4M ATTORNEYJ' Patented May 21, 1929.

UNITED STATES PAraN'r OFFICE.

HOWARD D. SAYLOR, OF NEWARK, NEW JERSEY, ASSIGNOR 'lO DRIVER-HARRIS COM- PANY, OF HARRISON, NEW JERSEY, A GORPQRATION OF NEW JERSEY.

INSULATED CONDUCTOR.

Application filed October 28, 1924. Serial No. 748,285.

My invention relates to insulated conductors and has for its object to produce a new and improved insulated conductor which is more durable in use and less expensive in manufacture than present insulated conductors. It also has for its object to produce an improved insulated conductor which is especially adapted for use in making heater cords.

Heretofore heater cord conductors have ordinarily consisted of a strand of braided or grouped copper wires, which strand was wrapped with a winding of cotton thread and then passed through a rubber coating device or tubing machine which deposited the tube of rubber upon the cotton, the rubber being subsequently surrounded by braided or wrapped asbestos, which was then covered by one or more sheaths of braided cotton or silk, or two of the asbestos covered elements were twisted together and then covered by one or more sheaths of braided cotton or silk.

The foregoing method involves the cost of the cotton winding and the step of applying it, this cotton winding being necessary to prevent the wires of the conductor from penetrating the rubber in case any of the copper strands should become broken so as to present free ends. Where the rubber was vulcanized, the cotton winding also separates the rubber from the copper so that the sulphur in the vulcanized rubber will not attack the copper to such an extent as it would if the cotton winding were absent.

The present invention permits the cotton winding to be omitted and results in having the rubber protect the asbestos, which asbestos in the old form, when the outer sheathing became broken, was readily worn away so as to reduce the insulation.

The following is a description of an embodiment of my invention, reference being had to the accompanying drawing, in which,

Figure 1 shows, on a somewhat enlarged scale, two insulated conductors each embodying my invention, the same being partly in elevation and partly in section; while,

Fig. 2 shows in a similar way a modification of the same.

Referring more particularly to the drawings, 2 represents a flexible strand or group of copper wires such as has been used heretofore in insulated conductors for heater cords. 4 is a sheath of asbestos yarn braided directly upon the strand 2 and loose thereon. 6 is a tubular film of rubber applied by an ordinary tubing machine and extending continuously around and along the asbestos covering 4 so as to protect the same against moisture and abrasion. 8 is a sheathing of textile fabric directly applied to the rubber film 6, this fabric being preferably braided thereon.

In the construction shown in Fig. 2, the partsare the same as in Fig. 1, with the exception that the asbestos as shown at 4 is wrapped directly about the conducting strand and the sheathing 8 surrounds two of the rubber coated asbestos covered conductors so as to contact directly with the rubber of both of them.

As stated above, the rubber is applied to the asbestos by means of an ordinary tubing machine. After the rubber is applied, it is submerged in water so as to cause the rubber to set and is then subjected to talcum powder or the like so as to give it a finished surface.

The rubber which is applied by the tubing machine is preferably made up of 30 pounds of reclaimed rubber, 25 pounds of powdered whiting, 25 pounds of mineral rubber, which is a well known wax composition, and one pound of petrolatum. In the tubing operation this material, after being thoroughly ground and mixed, is heated until it becomes plastic. It is then applied by the tubing machine and adheres slightly to the superficial fibers of the asbestos. The compound when placed in the tubing machine is heated to a point that softens it so that it flows rather readily but is not liquefied. It does not become fluid so as to penetrate the asbestos sheathing and in that respect differs from the rubber solution sometimes used.

The rubber film is spaced away from the conductor so that it is correspondingly protected from heat when in use and protects the asbestos against wear. The asbestos in .turn not only protects the rubber from heat but prevents the rubber from being penetrated by any loose or broken ends in the conducting strand. The rubber sheath made of the composition described is not vulcanized. It is by extrusion from the tubing machine molded about the asbestos and is mechanically removable therefrom by peeling. It surrounds the asbestos so as to make it unnecesary to tie the asbestos adjacent to the end of the conductor so as to prevent its raveling. The rubber further furnishes a smooth surface to which the textile fabric sheath is applied, and on account of the smoothness of the rubber sheath, the fabric sheath will be much smoother and will wear longer than textilesheaths which are applied directly to braided or wrapped asbestos, which has a somewhat rough surface, presenting high spots where wear of the sheathing is likely to take place. Furthermore, the rubber by separating the asbestos from the outer sheathing produces a conductor of better appearance, since where the sheathing is directly applied to the asbestos, the asbestos, being fuzzy, is liable to work through the textile sheathing and penetrate it so as to produce a more or less fuzzy and uneven appearance.

In the drawings shown, the thickness of the rubber is shown somewhat exaggerated, it being necessary to use only enough rubber to form a durable continuous adhering coating. A rubber sheath having a thickness of between one sixty-fourth and one thirtysecond of an inch is suitable for ordinary heater cords With this conductor, the asbestos being applieddirectly to the conducting strand, which is of smaller diameter than a strand and sheathing comprising a rubber tube or of a rubber tube surrounding a cotton winding, less asbestos is necessary than in the old construction. This saving, on account of the cost of asbestos, is substantial. I make the asbestos sheath about one sixty-fourth of an inch thick.

Although in the new form more rubber is required for a given thickness of rubber and diameter of strand on account of the larger diameter of the base to which it is applied, that is relatively unimportant on account of the low cost of rubber. In the new type of construction the asbestos sheathing is thicker than the old cotton winding and on account of the greater separation of the rubber from the conductor thus secured, results in an increase in the life of-the insulated conductor.

As will be evident to those skilled in the art, my invention permits of various modifications without departing from the spirit thereof or the scope of the appended claims.

What I claim is:

1. A flexible insulated conductor comprising a flexible conducting core, a flexible covering of fibrous asbestos applied directly thereficial fibers only thereof, the film not exceeding one thirty-second of an inch in thickness.

- 2. A flexible insulated conductor comprising a flexible conducting core, a flexible covering of asbestos yarn applied directly thereto and loose thereon, and a non-vulcanizable tubular rubber film continuously surrounding said asbestos and removable therefrom, the film not exceeding one thirty-second of an inch in thickness.

3. A flexible insulated conductor comprising a flexible conducting core, a loose flexible covering of asbestos yarn braided thereon, and a non-vulcanizable tubular rubber film continuously surrounding said asbestos and adhering to the superficial fibers only thereof,'tl1e film not exceeding one thirty-second of an inch in thickness.

4-. A flexible insulated conductor comprising a flexible conducting core, a flexible covering of asbestos yarn applied directly thereto, a non-vulcanizable tubular rubber film continuously surrounding said asbestos and removable therefrom and a sheath of textile fabric directly in contact with said rubber film, the film not exceeding one thirtysecond of an inch in thickness.

5. A flexible insulated conductor comprising a flexible conducting core, a flexible covering of asbestos yarn applied directly thereto, a non-vulcanizable tubular rubber film continuously surrounding but not impregnating said covering, the rubber in all the conductor being spaced away from the core by the asbestos, the film not exceeding one thirty-second of an inch in thickness.

6. A flexible heater cord conductor comprising a flexible conducting core, a sheath of asbestos fiber applied about said core, rubber composition uniformly applied about the asbestos sheath in a suitably heated and viscous condition so that when cooled it takes the form of a flexible non-vulcanized film surrounding and not materially penetrating the fibers of'the asbestos, and a covering of textile material for said film.

HOWARD D. SAYLOR. 

